1. Field of the Invention
This invention relates generally to the field of insect inhibitory Bacillus thuringiensis proteins and, more particularly, to B. thuringiensis crystal proteins that inhibit Hemipteran and Coleopteran insects. Isolated polynucleotides and proteins, transgenic cells, parts, and plants and related methods that provide for inhibition of Hemipteran and Coleopteran insects are described. Also described are methods for combining the B. thuringiensis crystal proteins that inhibit Hemipteran and Coleopteran insects with distinct insect control agents to obtain increased levels of Hemipteran and Coleopteran insect inhibition, Hemipteran and Coleopteran insect resistance management, or an expanded spectrum of insect pest control.
2. Related Art
Bacillus thuringiensis Crystal Proteins
The Gram-positive soil bacterium Bacillus thuringiensis is well known for its production of proteinaceous parasporal crystals, or δ-endotoxins, that are toxic to a variety of Lepidopteran, Coleopteran, and Dipteran larvae. B. thuringiensis produces crystal proteins during sporulation which are specifically toxic to certain species of insects. Many different strains of B. thuringiensis have been shown to produce insecticidal crystal proteins, and compositions comprising B. thuringiensis strains which produce proteins having insecticidal activity have been used commercially as environmentally-acceptable insecticides because of their toxicity to the specific target insect, and non-toxicity to plants and other non-targeted organisms.
Commercial formulations of naturally occurring B. thuringiensis isolates have long been used for the biological control of agricultural insect pests. In commercial production, the spores and crystals obtained from the fermentation process are concentrated and formulated for topical foliar application according to conventional agricultural practices.
Several first toxins have been used commercially in plants. Unfortunately, the toxins that are currently available do not provide for control of all insect pests that continue to plague crop production. In particular, Hemipteran insects still must be controlled by use of chemical, (topically applied or soil applied) insecticides. The Hemipteran or “piercing/sucking” insects are especially damaging to plants in that they are also known to transmit damaging plant viruses and cause plants to be more susceptible to bacterial and fungal infection. There is thus a need for additional materials and methods that would permit inhibition of Hemipteran insect pests in crops. There is also a need to obtain several different types of Hemipteran insect control agents with distinct modes of action for use in transgenic plants as Hemipteran insect resistance management tools.
Additionally, there remains a need for compositions and methods useful in producing transgenic plants which express two or more different B. thuringiensis toxins toxic to the same insect species and which confer a level of resistance management for delaying the onset of resistance of any particular susceptible insect species to one or more of the insecticidal agents expressed within the transgenic plant. Alternatively, expression of a B. thuringiensis insecticidal protein toxic to a particular target insect pest along with a different agent toxic to the same insect pest but which confers toxicity by a different mode of action from that exhibited by the B. thuringiensis toxin is desirable. Such other different agents comprise Xenorhabdus sp. or Photorhabdus sp. insecticidal proteins, deallergenized and de-glycosylated patatin proteins or permuteins thereof, B. thuringiensis vegetative insecticidal proteins, lectins, approaches such as dsRNA-mediated gene suppression, and the like. One method for achieving this result would be to produce two different transgenic events, each event expressing a different insecticidal agent, and breeding the two traits together into a hybrid plant. Another method for achieving this result would be to produce a single transgenic event expressing both insecticidal agents. This can be accomplished by transformation with a nucleotide sequence that encodes two or more insecticidal agents, but another method would be to produce a single event that was transformed to express a first insecticidal agent, and then transform that event to produce a progeny event that expresses both the first and the second insecticidal agents.